JPH02194146A - High strength hot rolled steel sheet having excellent cold workability and surface quality and its manufacture - Google Patents
High strength hot rolled steel sheet having excellent cold workability and surface quality and its manufactureInfo
- Publication number
- JPH02194146A JPH02194146A JP7033789A JP7033789A JPH02194146A JP H02194146 A JPH02194146 A JP H02194146A JP 7033789 A JP7033789 A JP 7033789A JP 7033789 A JP7033789 A JP 7033789A JP H02194146 A JPH02194146 A JP H02194146A
- Authority
- JP
- Japan
- Prior art keywords
- less
- rolled steel
- hot
- strength
- steel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 130
- 239000010959 steel Substances 0.000 title claims abstract description 130
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 238000005098 hot rolling Methods 0.000 claims abstract description 14
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 12
- 229910052802 copper Inorganic materials 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 5
- 238000004804 winding Methods 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 10
- 229910052758 niobium Inorganic materials 0.000 claims description 8
- 229910000859 α-Fe Inorganic materials 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 abstract description 10
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 5
- 229910052710 silicon Inorganic materials 0.000 abstract description 4
- 238000010438 heat treatment Methods 0.000 description 50
- 239000010949 copper Substances 0.000 description 46
- 238000003466 welding Methods 0.000 description 20
- 238000012545 processing Methods 0.000 description 14
- 238000001556 precipitation Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 8
- 239000006104 solid solution Substances 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 238000005096 rolling process Methods 0.000 description 6
- 230000009466 transformation Effects 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000005728 strengthening Methods 0.000 description 4
- 230000032683 aging Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000001376 precipitating effect Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 208000010392 Bone Fractures Diseases 0.000 description 2
- 206010017076 Fracture Diseases 0.000 description 2
- 229910001563 bainite Inorganic materials 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 229910052738 indium Inorganic materials 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 241000270281 Coluber constrictor Species 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 241000270666 Testudines Species 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- OQZCSNDVOWYALR-UHFFFAOYSA-N flurochloridone Chemical compound FC(F)(F)C1=CC=CC(N2C(C(Cl)C(CCl)C2)=O)=C1 OQZCSNDVOWYALR-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000005554 pickling Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【発明の詳細な説明】
[産業上の利用分野]
本発明は極めて加工度の高い成形性と同時に高い製品の
強度が要求される利用分野に提供する熱延鋼板およびそ
の製造方法に関するものである。[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a hot-rolled steel sheet and a method for manufacturing the same, which are used in fields of application that require extremely high formability and high product strength. .
[従来の技術]
従来の加工用熱延高強度鋼板は炭素間約0.03%以上
であり、その炭素を利用した焼入れによる組織強化のほ
かにMn、 Si、 P等の固溶体強化元素を添加した
り、TiやNb等の炭窒化物による析出強化を活用して
製造されるのが通常である。[Conventional technology] Conventional hot-rolled high-strength steel sheets for processing have a carbon content of approximately 0.03% or more, and in addition to strengthening the structure by quenching using carbon, solid solution strengthening elements such as Mn, Si, and P are added. Ordinarily, it is manufactured by utilizing precipitation strengthening with carbonitrides such as Ti and Nb.
このようにして得られた高強度鋼板は引張強さが高くな
るに従い加工性、特に延性が低くなっていく。従って高
強度と同時に高い加工性を確保することはできない。As the tensile strength of the high-strength steel plate obtained in this manner increases, the workability, especially the ductility thereof, decreases. Therefore, it is not possible to ensure high strength and high workability at the same time.
高強度と同時に高い加工性を確保しなければならないと
いう相矛盾する・B!ll!に十分に応える技術は見当
たらない。一つの理想と思われる技術は、冷間加工変形
をするときは鋼板の強度が低いと同時に加工性、特に延
性が十分に高く、加工が終了した後にその加工品の強度
が高くなるとすれば最終製品として複雑な加工部品にな
ると共に強固な部品になることになる。この考え方に従
った技術の例は1例えば、特公昭57−17049号公
報などにみられる。この場合では、Cuの固溶状態から
それの析出状態への変化を利用している。即ち、強度の
。It is contradictory that high strength and workability must be ensured at the same time - B! ll! There is no technology that can adequately respond to this. One ideal technology is that when performing cold deformation, the strength of the steel sheet is low, and at the same time, the workability, especially ductility, is sufficiently high, and the strength of the processed product is high after the deformation is completed. As a product, it becomes a complex machined part and a strong part. An example of a technique based on this idea can be found in, for example, Japanese Patent Publication No. 17049/1983. In this case, the change from the solid solution state of Cu to its precipitated state is utilized. i.e. of strength.
低いうちに加工しておき、その後の熱処理によってCu
を析出させることによって加工部品の強度を上げようと
するものである。Process it while it is still low, and then heat treat it to reduce Cu.
The aim is to increase the strength of processed parts by precipitating .
しかしながら、特公昭57−17049号公報に見られ
る固溶したCuを熱処理によって析出させ鋼板の強度を
あげることおよび熱処理条件等は古くから周知の技術で
ある。それは例えばA11oys of 1ronan
d copper (McGR八胃−へILL
ロ00に GOMPANY、Inc、。However, the technique of increasing the strength of a steel plate by precipitating solid-dissolved Cu by heat treatment and the heat treatment conditions, etc., as disclosed in Japanese Patent Publication No. 57-17049, have been well known for a long time. For example, A11oys of 1ronan
d copper (McGR Yasuga-he ILL
RO00 GOMPANY, Inc.
!934)に明記されている。! 934).
[発明が解決しようとする課題]
最近の高加工性熱延鋼板の材質特性に対する利用者側か
らの要求の度合は益々高くなりつつある。即ち、より一
層の高加工変形を必要とする複雑な形状部品が増えてい
ることと、鋼板の利用者側での変形加工工程を出来る限
り少なくして低コスト化を計る必要性が近年とみに増え
ているためである。従って、萌述の特公昭57−170
49号公報記載の技術内容では到底鋼板の利用者側の要
求を満たすものではない。[Problems to be Solved by the Invention] Recently, the degree of demand from users for the material properties of highly workable hot-rolled steel sheets is becoming higher and higher. In other words, the number of parts with complex shapes that require even higher processing deformation is increasing, and the need to reduce costs by minimizing the deformation process on the steel plate user side has increased in recent years. This is because Therefore, Moesho's special public service in Sho 57-170
The technical content described in Publication No. 49 does not meet the requirements of steel sheet users.
利用者側からの高加工性熱延鋼板にたいする最近の強い
要求の一つは、最終製品の超高強度化である。例えば、
従来では引張強度で45kgf/mm’程度の部品を、
最近では60kgf/me’以上の強度を持った鋼板で
製造したいと言う要求である。従って、この鋼板の超高
強度化と同時に高加工性を同時に満たす技術を開発する
必要がある。One of the recent strong demands from users for highly formable hot-rolled steel sheets is for the final product to have ultra-high strength. for example,
Conventionally, parts with a tensile strength of about 45 kgf/mm',
Recently, there has been a demand for manufacturing from steel plates with a strength of 60 kgf/me' or more. Therefore, it is necessary to develop a technology that simultaneously increases the strength of this steel sheet and provides high workability.
その次は鋼板の変形加工時の極めて高い変形加工性能が
要求されていることである。これは最終部品の形状が益
々複雑になってきており、これに応えつる鋼板を提供し
なくてはならないことである。また、利用者側での加工
工程数を減らしたいという要望も強く、そのためにも極
めて高い変形加工性能をもった鋼板を提供しなくてはな
らなくなっている。Next is the need for extremely high deformation performance when deforming steel plates. This means that the shapes of final parts are becoming more and more complex, and that it is necessary to provide steel plates that meet these demands. In addition, there is a strong desire to reduce the number of processing steps on the user side, and for this purpose, it is necessary to provide steel sheets with extremely high deformation processing performance.
さらには、利用者側での熱処理工程のm+素化の必要性
である。当然、低コスト化を指向する部品メーカーとし
ては、短時間で熱処理が済み生産性を−層高める必要が
ある。Furthermore, there is a need for m+ elementization in the heat treatment process on the user side. Naturally, as a parts manufacturer aiming to reduce costs, it is necessary to be able to perform heat treatment in a short time and further increase productivity.
これらの最近の鋼板利用者側からの新しい鋼板にたいす
る要求に対して従来技術では満足に応えつるものはない
。本発明ではそれらの要求に応える冷間加工性および表
面品質の優れた高強度熱延鋼板およびその製造方法を開
発したものである。No conventional technology has been able to satisfactorily meet these recent demands for new steel sheets from steel sheet users. The present invention has developed a high-strength hot-rolled steel sheet with excellent cold workability and surface quality, and a method for manufacturing the same, to meet these demands.
[課題を解決するための手段コ
先ず、本発明の対象である加工用熱延鋼板について説明
する。[Means for Solving the Problems] First, the hot-rolled steel sheet for processing, which is the object of the present invention, will be explained.
本発明の加工用熱延鋼板は、以下の理由によりC0.0
005〜0.0+59b 、 Mn 0.05〜0.5
N 、 S0.001〜0.0:10 !k 、 C
u 1.0〜2.2 % 、 P 0.200%以下、
Si 1.0 ’*以下、 N 0.0050!4
以下、 Sol、A交0.002〜0.10 !4.
B 0.0002〜0.0030 %、その他年可避的
元素からなり、かつパーライトの発生を回避した主とし
てフェライト単相からなることを基本とし、これに必要
に応じてTi、 Nbの一種または二極を、更にはNi
を含有させる。The hot-rolled steel sheet for processing of the present invention has a C0.0 for the following reasons.
005~0.0+59b, Mn 0.05~0.5
N, S0.001~0.0:10! k, C
u 1.0-2.2%, P 0.200% or less,
Si 1.0'* or less, N 0.0050!4
Hereinafter, Sol, A ratio 0.002 to 0.10! 4.
B 0.0002 to 0.0030%, and other inevitable elements, and mainly consists of a single phase of ferrite avoiding the generation of pearlite, and if necessary, one or two of Ti and Nb are added. poles, and even Ni
Contain.
本発明者等は、Cu添加鋼に種々の元素を単独あるいは
複合添加した熱延鋼板の研究を行った結果、Cuの析出
による強度上昇量がCflにより変化し、Cuを低減す
ることによって従来知られていたCuの析出による強度
上昇量よりも遥かに大きな強度上昇量が得られる事を新
規に知見した。As a result of research on hot-rolled steel sheets in which various elements were added singly or in combination to Cu-added steel, the present inventors found that the amount of strength increase due to Cu precipitation changes with Cfl, and that by reducing Cu, conventionally known It was newly discovered that a much larger increase in strength can be obtained than the increase in strength due to the precipitation of Cu.
第1図はMn 0.15!に、 Si 0.02亀、
S 0.015tS、 P0.014に、 N 0.0
020!に、 Sol AfL0.03!に、 Cu
1.34 。Figure 1 shows Mn 0.15! In, Si 0.02 turtle,
S 0.015tS, P0.014, N 0.0
020! In, Sol AfL0.03! In, Cu
1.34.
B 0.0001を含む鋼を基本成分とし、Clを0.
0015%〜0.0465%の範囲で変化させた鋼を溶
製し、1050℃で加熱後、^3点以トで熱間圧延を終
了し板厚3.0in+とじ、300℃で巻き取った時の
Cuと引張強さの関係を示すグラフであり、図中、曲線
(a)は300℃で巻き取ったままの熱延鋼板の場合、
曲線(b)はその熱延鋼板を600℃で10分間熱処理
した場合を示す。曲線(a)と曲線(b)の差がCuの
析出による強度上昇量であり、clが0.025%以上
では強度上昇量は約15kg/m112であるのに対し
、C(itが0.01596以下では強度上昇量は約2
0kg/l11112と極めて大きな強度上昇量が得ら
れる。Cuが0.015!I、を境に巻き取ったままの
熱延鋼板の引張強さに大きな変化が認められるが、この
強度差はCの固溶強化だけでは説明できない。この強度
差に対応して、Cff1か0.0154kを境に巻き取
ったままの熱延鋼板の伸びにも大きな変化が認められる
。The basic component is steel containing 0.0001 B, and 0.000% Cl.
Steel with a change in the range of 0.015% to 0.0465% was melted, heated at 1050°C, hot rolled at ^3 points or more, bound to a plate thickness of 3.0in+, and rolled up at 300°C. It is a graph showing the relationship between Cu and tensile strength at 300°C.
Curve (b) shows the case where the hot rolled steel sheet was heat treated at 600°C for 10 minutes. The difference between curve (a) and curve (b) is the amount of increase in strength due to the precipitation of Cu. When Cl is 0.025% or more, the amount of increase in strength is about 15 kg/m112, while when C(it is 0. Below 01596, the strength increase is approximately 2
An extremely large increase in strength of 0 kg/l11112 can be obtained. Cu is 0.015! A large change in the tensile strength of the as-rolled hot rolled steel sheet is observed at I, but this strength difference cannot be explained only by the solid solution strengthening of C. Corresponding to this strength difference, a large change is observed in the elongation of the hot-rolled steel sheet as it is wound, starting from Cff1 or 0.0154k.
第2図は第1図と同じ1.Tl;C++含有熱延鋼板の
伸びとClの関係を示すグラフである。同図より、Cu
を0.0154に以下に制御1−る事により極めて高い
延性を確保し得る事が認められる。Figure 2 is the same as Figure 1. Tl; is a graph showing the relationship between elongation and Cl of a C++-containing hot rolled steel sheet. From the same figure, Cu
It is recognized that extremely high ductility can be ensured by controlling 1- to 0.0154 or less.
このようにctlが0.01!di以下の場合、延性が
高< rtつ熱処理による強度上昇量が大きくなる理由
は未だ明らかではないが、敢えて推測すれば以下の如く
考える事ができる。即ち、Cuは鋼中で偏析しCuの含
有量はフェライト中とパーライト中では異なり、パーラ
イト中の方が高い。このためパーライト中のCuはフェ
ライト中のCuに比べ平衡固溶度に対する過飽和度が大
きく析出し易い状態にある。従って300℃という低温
で巻き取った場合でも、Cuが高くパーライトか存在す
る場合にはCuが一部析出し硬質化する。これに対しC
uが低くパーライトが存在せずフェライト単相の場合に
は、CCJが過飽和な状態で固溶され硬質化しない。In this way, ctl is 0.01! The reason why the strength increase due to heat treatment is large when the ductility is high < rt is not yet clear when di or less, but if we dare to speculate, we can think of it as follows. That is, Cu segregates in steel, and the content of Cu is different between ferrite and pearlite, and is higher in pearlite. For this reason, Cu in pearlite has a higher degree of supersaturation relative to the equilibrium solid solubility than Cu in ferrite, and is in a state where it is more likely to precipitate. Therefore, even when wound at a low temperature of 300° C., if the Cu content is high and pearlite is present, some Cu will precipitate and become hard. On the other hand, C
When u is low and pearlite does not exist and there is a single ferrite phase, CCJ is dissolved in a supersaturated state and does not harden.
これらの熱延板を600″C程度の高温で熱処理すると
、過飽和状態にあったCuの十分な析出が起こり強度が
一卜昇するものと想定される。It is assumed that when these hot-rolled sheets are heat-treated at a high temperature of about 600''C, sufficient precipitation of Cu, which was in a supersaturated state, occurs, resulting in a further increase in strength.
この様にCuは極めて高い強度上昇量と極めて高い延性
を確保するためには極力低減させることが必要である。In this way, it is necessary to reduce Cu as much as possible in order to ensure an extremely high increase in strength and extremely high ductility.
Cuの下限は工業的に溶製しつる限界の0.0005%
とする。逆にCuが0.015’4を超えると強度上昇
量と延性はさがると同時に、加工前の鋼板を製造すると
きに熱延の巻き取り温度に対する制限が発生する。即ち
、焼入れ組織が発生して加工前の鋼板の延性を下げるか
らである。従って、Cuは0.0005〜0.0154
にの範囲とする。The lower limit of Cu is 0.0005%, which is the limit for industrial melting.
shall be. On the other hand, if Cu exceeds 0.015'4, the amount of increase in strength and ductility will decrease, and at the same time, there will be restrictions on the winding temperature of hot rolling when manufacturing a steel plate before processing. That is, this is because a hardened structure is generated and reduces the ductility of the steel sheet before processing. Therefore, Cu is 0.0005 to 0.0154
The range shall be .
特に好ましいCuは、製鋼能力にもよるが、0.000
5〜0.00504にである。Particularly preferable Cu is 0.000
5 to 0.00504.
これに対し、前述の特公昭57−17049号では、C
uは、その実m例によりば、 0.04!4が開示され
、モして熱延ままの鋼板の伸びは37.9% 、引張強
さは38.Ikg/mm2である。一方、550℃X1
llrの熱処理による強度、ト昇mは13.9kg/m
a+2である。これは上記公報に示す発明におけるC3
31では、本発明に反して、組織としてパーライト相が
存在するため、熱延ままの段階でも既にCuが一部析出
しており、延性が本発明より著しく低く、且つ熱処理に
よる強度上昇量も著しく少ないものである。On the other hand, in the aforementioned Special Publication No. 57-17049, C.
According to an actual example, u is 0.04!4, and the elongation of the as-hot-rolled steel sheet is 37.9%, and the tensile strength is 38. Ikg/mm2. On the other hand, 550℃
Strength due to heat treatment of llr, t rise m is 13.9 kg/m
It is a+2. This is C3 in the invention shown in the above publication.
In No. 31, contrary to the present invention, since a pearlite phase exists as a structure, some Cu has already precipitated even in the as-hot-rolled stage, and the ductility is significantly lower than that of the present invention, and the strength increase due to heat treatment is also significant. There are few.
本発明における熱処理後の強度向上の特徴点は、熱処理
による全体の強度上昇のみならず、局部加熱による成形
部品の局部的強度上昇が大きいことである。ここで局部
加熱とは1例えばスポット溶接、アーク溶接、フラッシ
ュバット溶接等の溶接および局部的加熱f段(例えば、
高エネルギービーム(レーサー、電子ビーム)照射、プ
ラズマ加熱、高周波加熱、バーナー加熱等)を意味する
。The characteristic feature of the strength improvement after heat treatment in the present invention is that not only the overall strength increase due to heat treatment but also the local strength increase of the molded part due to local heating is large. Here, local heating refers to 1. For example, welding such as spot welding, arc welding, flash butt welding, and local heating f-stage (for example,
(high-energy beam (racer, electron beam) irradiation, plasma heating, high-frequency heating, burner heating, etc.)
第3図は本発明鋼のスポット溶接部の断面硬さ分布を示
した図である。同図より本発明鋼は同一強度の比較鋼に
比べ、C量が少ないためナゲツト部の硬さが低いことお
よび熱影響部にCuの析出による硬さ上昇が認められる
。FIG. 3 is a diagram showing the cross-sectional hardness distribution of the spot welded portion of the steel of the present invention. The figure shows that the steel of the present invention has a lower hardness in the nugget part due to a smaller amount of C than the comparative steel of the same strength, and that the hardness increases due to the precipitation of Cu in the heat affected zone.
第4図は本発明鋼のスポット溶接部の十字引張強さを比
較鋼のそれと対比して示した図である。FIG. 4 is a diagram showing the cross tensile strength of a spot weld of the steel of the present invention in comparison with that of a comparative steel.
同図より、本発明鋼の十字引張強さは比較鋼のそれに比
べ極めて高く、適正溶接電流であるナゲツト径が5(T
(tは板厚)となる溶接電流時の十字引張強さで比べ
ると、2倍以上の強さを持つことが認められる。これは
第3図に示したように、熱影響部に認められるCuの析
出による硬さ上昇によるものであり1本発明鋼はスポッ
ト溶接のような掻く短時間の入熱によっても局部的な強
度上昇をはかり得る特性をもっている。From the figure, the cross tensile strength of the steel of the present invention is extremely high compared to that of the comparative steel, and when the nugget diameter, which is the appropriate welding current, is 5 (T
When comparing the cross tensile strength at a welding current of (t is the plate thickness), it is recognized that the strength is more than twice as strong. As shown in Figure 3, this is due to an increase in hardness due to the precipitation of Cu observed in the heat-affected zone.1 The steel of the present invention has a high local strength even with short-term heat input such as spot welding. It has the property of being able to rise.
第5図は本発明鋼にレーザーを照射した時の、鋼板の硬
さの変化におよぼすレーザー照射回数の影響を示した図
である。レーザー照射条件はCO2ガスレーザ−、lo
kw、 lOx 10mmビーム、照射時間0.05秒
、照射間隔6秒である。数回のレーザー照射により硬さ
は大きく上昇している。FIG. 5 is a diagram showing the effect of the number of laser irradiations on the change in hardness of a steel plate when the steel of the present invention is irradiated with a laser. Laser irradiation conditions are CO2 gas laser, lo
kW, lOx 10 mm beam, irradiation time 0.05 seconds, irradiation interval 6 seconds. The hardness increases significantly after several laser irradiations.
一般に、強度部材での破壊危険部位は、ごく限られた部
分であることが多く、従って、部品全体の熱処理強化を
必要とすることは少ない。また、成形加工品の熱処理は
、生産性、コストの面から、短時間に、しかも連続的に
処理することが望ましい。従って破壊危険部位だけを短
時間の熱処理によって強化することの技術的意義は極め
て大きい。In general, the risk of fracture in a strength member is often in a very limited area, and therefore it is rarely necessary to strengthen the whole part by heat treatment. Further, from the viewpoint of productivity and cost, it is desirable that the heat treatment of the molded product be carried out in a short period of time and continuously. Therefore, it is of great technical significance to strengthen only the parts at risk of fracture by short-term heat treatment.
具体例の1つに自動車のホイールディスクがある。ホイ
ールは重要保安部品の1つであり、その寿命は材料の疲
労特性に支配される。ホイールの亀裂発生箇所はナツト
座、ハツト部等の板厚方向歪の大きな部位、飾り穴部、
ボルト穴部等の剪断された穴の縁およびディスクとリム
のスポット溶接部であり、ここでの疲労強度が重要であ
る。One specific example is an automobile wheel disc. Wheels are one of the important safety parts, and their service life is controlled by the fatigue properties of the materials. Cracks occur in areas where there is large strain in the plate thickness direction such as the nut seat and the hat, decorative holes,
These are the edges of sheared holes such as bolt holes and spot welds between the disc and the rim, where fatigue strength is important.
第6図は本発明鋼板の熱処理(600℃x30秒)前後
の疲労強度を調査した結果を示した図である。FIG. 6 is a diagram showing the results of investigating the fatigue strength of the steel plate of the present invention before and after heat treatment (600° C. x 30 seconds).
比較材にくらべ、本発明鋼は疲労強度が高く、特に熱処
理後はその引張り強さが上昇した結果、極めて高い疲労
強度をもっている。前述のホイールにおける疲労亀裂発
生危険箇所に局部加熱を施すことによって、著しい寿命
の延長がはかられ得る。Compared to comparative materials, the steel of the present invention has high fatigue strength, and especially after heat treatment, its tensile strength increases, resulting in extremely high fatigue strength. By applying localized heating to the points in the wheel where fatigue cracks are likely to occur, the life of the wheel can be significantly extended.
Pは鋼板の強度および耐食性を向上させる元素として有
効であるが、その必要がないときは、P量は0.0:1
%以下であってもよい。一方、鋼板の強度および耐食性
を向上させる場合には、0.06〜0.20!にのPの
添加が好ましい。これは、後述の如く、Bの添加により
耐二次加工割れ性が向上することから、Bを添加しない
場合に比べてPの添加量を多くできるが、それでも0.
20Hを超えると鋼板の二次加工割れが発生するのでそ
れを上限とする。尚、Pの添加はCuの添加とともに鋼
板の耐食性能を高めるのに有効である。P is effective as an element to improve the strength and corrosion resistance of steel sheets, but when it is not necessary, the amount of P is 0.0:1.
% or less. On the other hand, when improving the strength and corrosion resistance of steel plates, 0.06 to 0.20! It is preferable to add P to . This is because, as will be described later, the addition of B improves the secondary processing cracking resistance, so the amount of P added can be increased compared to the case where B is not added, but still 0.
If it exceeds 20H, secondary processing cracks will occur in the steel plate, so this is set as the upper limit. Note that the addition of P is effective in improving the corrosion resistance of the steel sheet along with the addition of Cu.
Siは通常、不純物としては、0.03%以下含まれる
が、綱板の強度を上げる元素としてその必要強度レベル
に応じて1.0%以下、好ましくは0.3〜t、o*7
4加する。しかし、1.0tを超えると熱間圧延工程に
おけるスケールの発生が著しく、tA板の表面性状を劣
化させるためその上限を1.0%とする。Si is normally contained as an impurity in an amount of 0.03% or less, but as an element that increases the strength of the steel plate, it is contained in an amount of 1.0% or less, preferably 0.3 to t, o*7, depending on the required strength level.
Add 4. However, if it exceeds 1.0 t, scale will occur significantly during the hot rolling process and the surface quality of the tA plate will deteriorate, so the upper limit is set at 1.0%.
MnおよびS量は鋼板の加工性を高めるためには低いほ
うが好ましく、それぞれの上限を0.5%。In order to improve the workability of the steel plate, it is preferable that the amounts of Mn and S be as low as possible, and the upper limit of each is set at 0.5%.
0.030%とし、好ましくは、それぞれ0.05〜0
.30!!。0.030%, preferably 0.05 to 0
.. 30! ! .
0.001〜0.010!にとする。 Mn量があまり
低くなりすぎると鋼板の表面疵が発生し易くなるのでそ
の下限を0.05!eiとする。0.001~0.010! Totosu. If the Mn content is too low, surface flaws will easily occur on the steel plate, so the lower limit is set at 0.05! Let it be ei.
Nfiは加工性を高めるためにも低いほうが好ましく
0.005096以下とする。Lower Nfi is preferable to improve workability.
It shall be 0.005096 or less.
Cupは加工前では固溶状態にしておき、加工後の熱処
理によりCuを析出させて強度をあげる。第7図は極低
炭素鋼にCuを添加した鋼の熱処理時間(熱処理温度5
50℃)による強度上昇量(熱処理後の引張強さ一熱延
まま引張強さ)をCuをパラメータとして示すグラフで
あり、図中、曲線(a)はCu 2.OH,曲線(b)
はCu 1.68!曲線(c)はCuL38*、曲線(
d)はCu 0.7144の場合である。同図よりCu
1.0%未満では曲線(d)の如く強度の上昇量は不
十分である。一方2.2本を超えると表面品質が劣化す
るので、Cuは1.0〜2.2t、好ましくは1.2〜
2.0tの範囲とする。The Cup is kept in a solid solution state before processing, and the strength is increased by precipitating Cu by heat treatment after processing. Figure 7 shows the heat treatment time (heat treatment temperature 5
50°C) is a graph showing the amount of increase in strength (tensile strength after heat treatment - tensile strength as hot rolled) with Cu as a parameter; in the figure, curve (a) is Cu2. OH, curve (b)
is Cu 1.68! Curve (c) is CuL38*, curve (
d) is the case of Cu 0.7144. From the same figure, Cu
If it is less than 1.0%, the amount of increase in strength is insufficient as shown in curve (d). On the other hand, if the number exceeds 2.2, the surface quality will deteriorate, so Cu should be 1.0 to 2.2t, preferably 1.2 to 2.2t.
The range is 2.0t.
A見は脱酸に必要な元素であり、Sol 、Aiが0.
002!Ii未満では脱酸が十分ではなく、一方多過ぎ
るとアルミナ生成量が増え、鋼の表面品質に悪影晋を与
えるので、その上限を0.1096とする。A is an element necessary for deoxidation, and Sol and Ai are 0.
002! If it is less than Ii, deoxidation will not be sufficient, while if it is too much, the amount of alumina produced will increase, which will have a negative impact on the surface quality of the steel, so the upper limit is set at 0.1096.
Bは本発明鋼板の表面品質を良好に保つために、重要な
元素である。本発明鋼の熱延において、圧延終了温度は
鋼板の材質を良好に保つ為^「3以上であることが必要
である。しかるに、前述の如<Cuの固溶もしくは析出
を制御するためにはCを0.01!d、以下とすること
が必要であり、(1の低下と共に鋼のAr3点は高くな
り、圧延終了温度を高くする必要がある。しかし、圧延
終了温度を高くすることは、圧延中に生成されるスケー
ル闇の増加をひきおこし、このスケールに起因する敗砂
状の疵が鋼板表面に発生する。従って材質と表面品質の
良好な鋼板を得るには、低炭素鋼のAr、変態点を下げ
る元素の添加が必要である。B is an important element in order to maintain good surface quality of the steel sheet of the present invention. In hot rolling of the steel of the present invention, the rolling end temperature must be 3 or higher in order to maintain good material quality of the steel plate.However, as mentioned above, in order to control solid solution or precipitation of Cu, It is necessary to keep C to 0.01!d or less, and (as C decreases, the Ar3 point of the steel increases, so it is necessary to raise the rolling end temperature. However, increasing the rolling end temperature , which causes an increase in the scale darkness generated during rolling, and this scale causes sand-like flaws to occur on the steel plate surface.Therefore, in order to obtain a steel plate with good material and surface quality, it is necessary to use Ar for low carbon steel. , it is necessary to add elements that lower the transformation point.
本発明者らはこの観点から、 Cuを添加した極低炭素
鋼のAr3におよぼず元素の影習を検討し、Bの添加に
よってAr3点が大幅に低下することを知見した。From this point of view, the present inventors investigated the influence of elements other than Ar3 in ultra-low carbon steel to which Cu was added, and found that the addition of B significantly lowers the Ar3 point.
第8図は1.3!1IICuを含有したTi添加極低炭
素鋼のAr3におよぼすBの効果を示した図であり、1
000℃xlO分加熱後熱延時の冷却速度に相当する3
0℃/Sの冷却速度で冷却した時のAr3点測定結果で
ある。Figure 8 is a diagram showing the effect of B on Ar3 of Ti-added ultra-low carbon steel containing 1.3!1IICu;
3, which corresponds to the cooling rate during hot rolling after heating to 000°C
These are the results of Ar 3-point measurement when cooling at a cooling rate of 0° C./S.
図かられかるように、0.0010tまでのBの添加に
よりAr3点は急激に低下し、それ以上の添加によりA
r3点は緩やかに低下する。As can be seen from the figure, the Ar3 point decreases rapidly with the addition of B up to 0.0010t, and with further addition
The r3 point gradually decreases.
第9図は、第8図の鋼を5加工話起による変態点の上昇
を考J、I!!シてそれぞれの鋼の^r、+30℃の温
度で圧延を終了した鋼板の散砂状スケール疵の発生状況
を示す図である。(1,0002!を以上のBの添加に
より、疵の発生は防止されており、このため下限を0.
0002%とする。一方、0.0030亀を超えるBの
添加はコスト的に不利である。なお、この範囲のBの添
加は2次加工割れ性を向上させる上でも好ましい。Figure 9 shows the increase in the transformation point of the steel shown in Figure 8 due to 5 processing steps.J,I! ! FIG. 3 is a diagram showing the occurrence of sand-like scale flaws in steel plates that have been rolled at a temperature of +30° C. for each steel. (By adding more than 1,0002! of B, the occurrence of scratches is prevented, so the lower limit is set to 0.
0002%. On the other hand, adding more than 0.0030 mm of B is disadvantageous in terms of cost. Note that addition of B in this range is also preferable in terms of improving secondary processing cracking resistance.
Ti、 Nbの一種また二種をそれぞれ0.旧〜0.2
96゜0.005〜0.2tの範囲で添加すると、Cと
Nはこれらによって固定され、得られる鋼板は非時効性
の鋼板になる。非時効性鋼板になると時効による延性の
低下はなくなり、−層の高延性鋼板が得られることにな
る。One or both of Ti and Nb were added at 0.0% each. Old ~ 0.2
When C and N are added in the range of 0.005 to 0.2 t at 96°, C and N are fixed, and the resulting steel sheet becomes a non-aging steel sheet. When the steel sheet becomes a non-aging steel sheet, there is no decrease in ductility due to aging, and a high ductility steel sheet with a negative layer is obtained.
Tiは鋼中のC,0,N、Sなどと反応するので、これ
らの量と併せ考えねばならないが、これらの元素を固定
し、高度のプレス加工性を得るためには0.01!に以
上の添加が必要であり、一方0.2*より多くすること
はコスト的に不利である。Ti reacts with C, 0, N, S, etc. in steel, so it must be considered in conjunction with the amount of these elements, but in order to fix these elements and obtain a high degree of press workability, the amount is 0.01! On the other hand, adding more than 0.2* is disadvantageous in terms of cost.
Nbも鋼中のC,0,Nなどと反応するので、これらの
頃と併せ考えねばならないが、これらの元素を固定し、
高度のプレス加工性を得るためには0.0005%以上
の添加が必要であり、一方0.2tより多くすることは
コスト的に不利である。Nb also reacts with C, 0, N, etc. in steel, so it must be considered in conjunction with these times, but by fixing these elements,
In order to obtain a high degree of press workability, it is necessary to add 0.0005% or more, while adding more than 0.2 t is disadvantageous in terms of cost.
Niは鋼板の表面品質を高品位に保ち、熱間脆性を防止
するのに有効である。必要に応じて0.15〜1.05
1i添加してもよい。Ni is effective in maintaining high quality surface quality of steel sheets and preventing hot embrittlement. 0.15-1.05 as necessary
1i may be added.
Cu添加鋼の熱間脆性は鋼表面に生成したスケールの下
に形成されるCu濃縮部が、その融点以上に加熱される
ことによって液状となり、オーステナイト粒界に浸透す
ることによって引き起こされる。したがってスラブの熱
延段階での熱間脆性を防止するには、Cu濃縮部の融点
以下で加熱することが理想であり、 ゛l080℃以下
の加熱が望ましい。The hot embrittlement of Cu-added steel is caused by the Cu-enriched area formed under the scale generated on the steel surface becoming liquid when heated above its melting point and penetrating into the austenite grain boundaries. Therefore, in order to prevent hot embrittlement during the hot-rolling stage of the slab, it is ideal to heat the slab to a temperature below the melting point of the Cu-enriched portion, and preferably to a temperature below 1080°C.
しかし、加熱温度の低下は圧延荷重の増加をもたらすた
め、圧延機の性能によりては必ずしも、1080℃以下
の加熱は実施できない。この場合にはNiの添加が有効
である。Niの添加により、上記のCu濃縮部にNiも
濃縮され、Cu濃縮部の融点をあげる。Niの0.15
%未満の添加ではその効果は小さく、一方1.Hを超え
るNiの添加はコスト的に不利である。However, since a decrease in heating temperature brings about an increase in rolling load, heating to 1080° C. or lower cannot necessarily be carried out depending on the performance of the rolling mill. In this case, adding Ni is effective. By adding Ni, Ni is also concentrated in the Cu-concentrated section, raising the melting point of the Cu-concentrated section. 0.15 of Ni
The effect is small if the addition amount is less than 1. Addition of Ni in excess of H is disadvantageous in terms of cost.
以上述べたTi、 Nbの一種または二種の添加、Ni
の添加は単独で添加しても、それらの二種以上を複合添
加しても効果を発揮する。Addition of one or two of Ti and Nb mentioned above, Ni
Even if they are added singly, or two or more of them are added in combination, the effect is exerted.
次に本発明鋼板の製造方法における熱間圧延工程につい
てであるが、連鋳機から直送された高温鋳片または、加
熱によってえられた高温鋳片をAr3以上の温度で熱間
圧延をおこない、その後、500℃以下の温度で巻き取
る。500℃を超える温度で巻取るとCuの析出が起こ
り、加工性の良い軟質鋼板が得られないのみならず、熱
処理による強度上昇量が小さくなる。本発明ではclを
制限して巻取段階でのCuの析出を抑ルノしており、5
00℃以下の温度で巻取ることにより大部分のCuを過
飽和固溶の状態に保ちつる。しかし500℃を超える温
度で巻取るとCuの析出が起こり硬質化するため、巻取
り温度の1限を500℃とする。全てのCuを固溶状態
に保つには巻取温度を350℃以下にすることが最適で
ある。従来の鋼のようにC量もしくはMn1lが高い場
合には、低温で巻取るとマルテンサイト相もしくはベイ
ナイト相という変態による硬質相が生成し硬質化するた
め、これを避けるために巻取温度に下限を設けなければ
ならない。Next, regarding the hot rolling process in the method for manufacturing the steel plate of the present invention, hot rolling is performed on a hot slab directly delivered from a continuous casting machine or a hot slab obtained by heating at a temperature of Ar3 or higher, Thereafter, it is wound up at a temperature of 500°C or less. If coiling is carried out at a temperature exceeding 500° C., precipitation of Cu will occur, and not only will a soft steel sheet with good workability not be obtained, but the amount of increase in strength due to heat treatment will be small. In the present invention, cl is limited to suppress Cu precipitation at the winding stage, and 5
By winding at a temperature of 00° C. or lower, most of the Cu is kept in a supersaturated solid solution state. However, if it is wound at a temperature exceeding 500°C, Cu will precipitate and become hard, so the first limit of the winding temperature is set at 500°C. In order to keep all of the Cu in a solid solution state, it is optimal to keep the winding temperature at 350° C. or lower. If the C content or Mn1l is high as in conventional steel, if it is rolled at a low temperature, a hard phase called martensite phase or bainite phase will be formed due to transformation and become hard, so to avoid this, a lower limit is set for the coiling temperature. must be established.
本発明鋼はC量およびMniを低く制御し、焼き入れ性
を著しく抑えているため巻取温度の冶金学的な下限温度
はない。但し、100℃未満で巻取ると巻形状が悪くな
り、これに起因する表面品質の劣化を招くため、好まし
くは巻取温度を350℃以下、100℃以りとする。In the steel of the present invention, the C content and Mni are controlled to be low, and the hardenability is significantly suppressed, so there is no metallurgical lower limit temperature for the coiling temperature. However, if the winding temperature is lower than 100°C, the winding shape will become poor, resulting in deterioration of surface quality, so preferably the winding temperature is 350°C or lower and 100°C or higher.
これに対して前掲の特公昭57−17049号によれば
、巻取温度を350℃以)1(450℃以下)に限定さ
れている。これは、350℃以下の低温では、相変態(
マルテンサイトもしくはベイナイト変態)が生じるため
に加工性が劣化する観点より限定しているものである。On the other hand, according to the above-mentioned Japanese Patent Publication No. 57-17049, the winding temperature is limited to 350° C. or higher) 1 (450° C. or lower). At low temperatures below 350°C, phase transformation (
This is limited because processability deteriorates due to the occurrence of martensite or bainite transformation.
しかるに、上記の如く本発明では極低炭素領域に限定し
ているので、巻取温度として350℃以下を採用しても
相変態がおこらず、従って加工性の問題がないので、前
掲の従来例よりも、Cuの固溶11の多い低温巻取が採
用できるものである。However, as mentioned above, since the present invention is limited to the extremely low carbon region, phase transformation does not occur even if the winding temperature is 350°C or lower, and therefore there is no problem in workability. Rather, low-temperature winding with a large amount of Cu in the solid solution 11 can be adopted.
得られた熱延板は成形加工後に熱処理を施してその強度
を高めるが、熱処理作業性からみると出来るだけ低温で
然も短時間の熱処理で終了させることが極めて大切であ
る。本発明ではこの点についても十分な検討を加え、短
時間の熱処理でその目的が達成されるようにしたもので
ある。The obtained hot-rolled sheet is subjected to heat treatment after forming to increase its strength, but from the viewpoint of heat treatment workability, it is extremely important to complete the heat treatment at as low a temperature as possible and in a short time. In the present invention, sufficient consideration has been given to this point, and the object is achieved with a short heat treatment.
例えば熱処理温度は750℃以下、熱処理時間は30分
以下といった短時間でその目的が十分に達せられる。For example, the purpose can be sufficiently achieved in a short time such that the heat treatment temperature is 750° C. or less and the heat treatment time is 30 minutes or less.
本発明鋼板は、例えば自動車のフレーム、ホイール1、
補強部品や圧力容器、コンプレッサーカバー、軸受けの
ような用途が考えられる。The steel plate of the present invention can be used, for example, in automobile frames, wheels 1,
Possible applications include reinforcing parts, pressure vessels, compressor covers, and bearings.
[実施例] 次に実hh例をあげて本発明を具体的に説明する。[Example] Next, the present invention will be specifically explained using an actual hh example.
実施例1
第1表に示したAがらMまでの鋼片を同表に示す加熱温
度で加熱熱延し、巻き取り、板厚4.On+mの熱延鋼
板を得た。その鋼板の引張試験値および、600℃で1
0分間の熱処理による引張強さのL昇量ΔTS(熱処理
後の引張強さ一熱延まま引張強さ)および散砂状スケー
ル疵の発生の有無を第1表に示す。本発明鋼AからHお
よびり、Mは優れた延性をもワており、短時間の熱処理
で引張強さが著しく上昇していると同時に散砂状スケー
ルの発生もない。これに対し比較鋼■は表面品質は良好
であるがC量が高く延性が低いのみならず、熱処理によ
る引張強さの上昇量も小さい。一方、比較鋼Jおよびに
は、優れた機械的性質をもっているが、数秒状スケール
疵が発生している。Example 1 Steel slabs from A to M shown in Table 1 were heated and hot-rolled at the heating temperatures shown in the same table, and rolled up to a thickness of 4. A hot rolled steel sheet of On+m was obtained. Tensile test value of the steel plate and 1 at 600℃
Table 1 shows the increase in tensile strength ΔTS (tensile strength after heat treatment - tensile strength as hot rolled) due to heat treatment for 0 minutes and the presence or absence of sand-like scale defects. The steels A to H and M of the present invention also have excellent ductility, and their tensile strength increases markedly after a short heat treatment, and at the same time, there is no occurrence of sand-like scale. On the other hand, comparative steel (3) has good surface quality, but not only has a high C content and low ductility, but also has a small increase in tensile strength due to heat treatment. On the other hand, Comparative Steels J and J had excellent mechanical properties, but had several second scale defects.
実施例2
第2表に示す組成の鋼NotおよびNo2を熱間圧延し
て板厚3.0ausの熱延鋼板を得た。これらの鋼板を
圧力容器に成形加工した。この圧力容器から、サンプル
を切り出した。切り出したサンプルの板厚子は約26t
であった。このサンプルのままの引張強さおよび630
℃で5分間の熱処理(圧力容器の内部応力を除去する応
力除去焼鈍に相当)後の引張強さを第3表に示す。同表
中の強度上昇量ΔTSは、プレス成形および熱処理後の
引張強さから、熱延ままの引張強さを引いた値である。Example 2 Steels Not and No2 having the compositions shown in Table 2 were hot rolled to obtain hot rolled steel plates having a thickness of 3.0 aus. These steel plates were formed into a pressure vessel. A sample was cut out from this pressure vessel. The thickness of the cut sample is approximately 26 tons.
Met. Tensile strength of this sample as is and 630
Table 3 shows the tensile strength after heat treatment at ℃ for 5 minutes (corresponding to stress relief annealing to remove the internal stress of the pressure vessel). The strength increase amount ΔTS in the same table is the value obtained by subtracting the tensile strength as hot rolled from the tensile strength after press forming and heat treatment.
比較鋼は加工後の熱処理により大幅に軟化しているのに
対し、本発明鋼は加工後の熱処理により更なる強度上昇
が達成されている。While the comparative steel was significantly softened by the heat treatment after working, the steel of the present invention achieved a further increase in strength by the heat treatment after working.
実施例3
第4表に示す組成の鋼No3およびNo4を熱間圧延し
て板厚2.0m111の熱延鋼板を得た。これらの鋼板
を酸洗後、サンプルを切り出しスポット溶接を行った。Example 3 Steels No. 3 and No. 4 having the compositions shown in Table 4 were hot rolled to obtain hot rolled steel plates with a thickness of 2.0 m111. After pickling these steel plates, samples were cut out and spot welded.
スポット溶接条件を第5表に示す。スポット溶接部の評
価をするために、各溶接電流での剪断引張強度、上室引
張強度、ナゲツト径を測定すると同時に、ナゲツト径が
5F【「となる溶接電流でスポット溶接したサンプルの
断面硬さ分布測定を行った。Table 5 shows the spot welding conditions. In order to evaluate spot welds, we measured the shear tensile strength, upper chamber tensile strength, and nugget diameter at each welding current, and at the same time measured the cross-sectional hardness of the sample spot welded at a welding current that made the nugget diameter 5F. Distribution measurements were performed.
第 5 表 スポット溶接条件
第3図は上記のサンプルの断面硬さ分布測定結果であり
、本発明鋼は溶接熱影背部にCuの析出に対応する硬さ
の一■二昇が認められる。第4図は各溶接電流での十字
引張強さの測定結果である。本発明鋼は溶接電流の小さ
い時から高い十字引張強さをもっており、適正な溶接電
流値であるナゲツト径が5rK可となる電流値での十字
引張強さで比較すると、本発明鋼のそれは比較鋼のそれ
に比べ2倍以」二の優第1た強さをもっている。第10
図は各溶接電流での剪断引張強さの測定結果である。本
発明鋼はいずれの溶接電流でも比較鋼にくらべ高い剪断
引張強度をもっている。Table 5 Spot Welding Conditions Figure 3 shows the cross-sectional hardness distribution measurement results of the above samples, and it is observed that the hardness of the steel of the present invention corresponds to the precipitation of Cu at the back of the welding heat shadow. FIG. 4 shows the measurement results of cross tensile strength at each welding current. The steel of the present invention has high cross tensile strength even when the welding current is small, and when comparing the cross tensile strength at a current value that allows the nugget diameter to be 5 rK, which is an appropriate welding current value, the steel of the present invention has a high cross tensile strength. It has a strength that is more than twice that of steel. 10th
The figure shows the measurement results of shear tensile strength at each welding current. The steel of the present invention has higher shear tensile strength than the comparative steel at any welding current.
[発明の効果]
本発明は、極めて良好な冷間加工性を有すると共に表面
品質に優れ、最終製品で必要とされる高い強度が冷間加
工後の短時間の熱処理により達成され得る新規な熱延鋼
板を提供するものであり、またかかる熱延鋼板を成分規
制および熱延鋼板の巻取温度の制御という簡便な手段に
より製造しつる新規な方法を提供するものであるから、
鋼板利用者側からの新たな要求に十分応えつるものであ
り、産業上碑益するところが極めて大である。[Effects of the Invention] The present invention provides a novel heat treatment method that has extremely good cold workability and excellent surface quality, and allows the high strength required for the final product to be achieved by a short heat treatment after cold working. The present invention provides a rolled steel sheet and a new method for producing such a hot rolled steel sheet by simple means of regulating the composition and controlling the coiling temperature of the hot rolled steel sheet.
It fully meets new demands from steel sheet users, and has enormous industrial benefits.
第1図は熱延鋼板の強度に及ぼすC量の影響を、Cuの
析出の為の熱処理の前後で示すグラフ、第2図は熱延鋼
板の延性に及ぼすC量の影響を示すグラフ、
第3図は本発明鋼板のスポット溶接部の断面の確さ分布
を示すグラフ、
第4図は本発明鋼板のスポット溶接部の十字引張強さに
およぼす溶接電流の影響を示すグラフ、第5図はレーザ
ー照射パス数による本発明鋼板の硬さの変化を示すグラ
フ、
第6図は本発明鋼板の疲労特性を熱処理航後で示すグラ
フ、
第7図は極低炭素鋼熱延鋼板の強度上昇量におよぼす熱
処理時間の影響をCu1ilをパラメータとして示すグ
ラフ、
第8図はCu添加極低炭素鋼のAr、点におよぼすBm
の影響を示すグラフ、
第9図は鋼板の表面品質におよぼすB量の影響を示すグ
ラフ、
第1n図は本発明鋼のスポット溶接部の剪断引張強さに
およぼす溶接電流の影響を示すグラフである。Figure 1 is a graph showing the effect of C content on the strength of hot rolled steel sheets before and after heat treatment for Cu precipitation. Figure 2 is a graph showing the effect of C content on the ductility of hot rolled steel sheets. Figure 3 is a graph showing the cross-sectional accuracy distribution of the spot weld of the steel plate of the present invention, Figure 4 is a graph showing the influence of welding current on the cross tensile strength of the spot weld of the steel plate of the present invention, and Figure 5 is a graph showing the influence of welding current on the cross tensile strength of the spot weld of the steel plate of the present invention. Graph showing the change in hardness of the steel plate of the present invention depending on the number of laser irradiation passes. Figure 6 is a graph showing the fatigue properties of the steel plate of the present invention after heat treatment. Figure 7 is the increase in strength of the ultra-low carbon hot rolled steel plate. A graph showing the effect of heat treatment time on Cuil as a parameter. Figure 8 shows the effect of Ar and Bm on Cu-added ultra-low carbon steel
Figure 9 is a graph showing the effect of B content on the surface quality of steel sheets; Figure 1n is a graph showing the effect of welding current on the shear tensile strength of spot welds of the steel of the present invention. be.
Claims (1)
イトの発生を回避した主としてフェライト単相からなる
ことを特徴とする冷間加工性および表面品質の優れた高
強度熱延鋼板。 2、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 Ni0.15〜1.0% N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% を含有し、残部Fe及び不可避的元素からなり、パーラ
イトの発生を回避した主としてフェライト単相からなる
ことを特徴とする冷間加工性および表面品質の優れた高
強度熱延鋼板。 3、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% に加えてTiまたはNbの一種をもしくは二種をそれぞ
れ0.01〜0.2%、0.005〜0.2%の範囲で
含有し、残部Fe及び不可避的元素からなり、パーライ
トの発生を回避した主としてフェライト単相からなるこ
とを特徴とする冷間加工性および表面品質の優れた高強
度熱延鋼板。 4、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 Ni0.15〜1.0% N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% に加えてTiまたはNbの一種をもしくは二種をそれぞ
れ0.01〜0.2%、0.005〜0.2%の範囲で
含有し、残部Fe及び不可避的元素からなり、パーライ
トの発生を回避した主としてフェライト単相からなるこ
とを特徴とする冷間加工性および表面品質の優れた高強
度熱延鋼板。 5、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% を含有し、残部Fe及び不可避的元素からなる鋼を、A
r_3以上の温度で熱間圧延し、得られた熱間圧延鋼帯
を500℃以下の温度で巻き取ることを特徴とする冷間
加工性および表面品質の優れた高強度熱延鋼板の製造方
法。 6、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 Ni0.15〜1.0% N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% を含有し、残部Fe及び不可避的元素からなる鋼を、A
r_3以上の温度で熱間圧延し、得られた熱間圧延鋼帯
を500℃以下の温度で巻き取ることを特徴とする冷間
加工性および表面品質の優れた高強度熱延鋼板の製造方
法。 7、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% に加えてTiまたはNbの一種もしくは二種をそれぞれ
0.01〜0.2%、0.005〜0.2%の範囲で含
有し、残部Fe及び不可避的元素からなる鋼を、Ar_
3以上の温度で熱間圧延し、得られた熱間圧延鋼帯を5
00℃以下の温度で巻き取ることを特徴とする冷間加工
性の極めて優れた高強度熱延鋼板の製造方法。 8、重量%で C0.0005〜0.015% Mn0.05〜0.5% S0.001〜0.030% Cu1.0〜2.2% P0.200%以下 Si1.0%以下 Ni0.15〜1.0% N0.0050%以下 Sol.Al0.002〜0.10% B0.0002〜0.0030% に加えてTiまたはNbの一種もしくは二種をそれぞれ
0.01〜0.2%、0.005〜0.2%の範囲で含
有し、残部Fe及び不可避的元素からなる鋼を、Ar_
3以上の温度で熱間圧延し、得られた熱間圧延鋼帯を5
00℃以下の温度で巻き取ることを特徴とする冷間加工
性の極めて優れた高強度熱延鋼板の製造方法。 9、熱間圧延後の巻取温度を350℃以下100℃以上
とすることを特徴とする冷間加工性の極めて優れた請求
項第5項〜第8項の何れか1項に記載の方法。[Claims] 1. C0.0005-0.015% Mn 0.05-0.5% S 0.001-0.030% Cu 1.0-2.2%, P 0.200% or less Si1 .0% or lessN0.0050% or lessSol. Cold workability characterized by containing 0.002-0.10% Al, 0.0002-0.0030% B, the remainder consisting of Fe and other unavoidable elements, and mainly consisting of a single ferrite phase that avoids the generation of pearlite. and high-strength hot-rolled steel sheets with excellent surface quality. 2. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less Ni0.15 ~1.0% N0.0050% or less Sol. Cold workability characterized by containing 0.002-0.10% Al, 0.0002-0.0030% B, the remainder consisting of Fe and other unavoidable elements, and mainly consisting of a single ferrite phase that avoids the generation of pearlite. and high-strength hot-rolled steel sheets with excellent surface quality. 3. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less N0.0050 % or less Sol. In addition to Al0.002-0.10% B0.0002-0.0030%, one or both of Ti or Nb are contained in the range of 0.01-0.2% and 0.005-0.2%, respectively. A high-strength hot-rolled steel sheet with excellent cold workability and surface quality, which is characterized by being mainly composed of a single phase of ferrite, with the balance being Fe and other unavoidable elements, and avoiding the generation of pearlite. 4. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less Ni0.15 ~1.0% N0.0050% or less Sol. In addition to Al0.002-0.10% B0.0002-0.0030%, one or both of Ti or Nb are contained in the range of 0.01-0.2% and 0.005-0.2%, respectively. A high-strength hot-rolled steel sheet with excellent cold workability and surface quality, which is characterized by being mainly composed of a single phase of ferrite, with the balance being Fe and other unavoidable elements, and avoiding the generation of pearlite. 5. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less N0.0050 % or less Sol. A steel containing 0.002 to 0.10% Al and 0.0002 to 0.0030% B, with the balance consisting of Fe and unavoidable elements.
A method for producing a high-strength hot-rolled steel sheet with excellent cold workability and surface quality, characterized by hot rolling at a temperature of r_3 or higher and winding the obtained hot-rolled steel strip at a temperature of 500°C or lower. . 6. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less Ni0.15 ~1.0% N0.0050% or less Sol. A steel containing 0.002 to 0.10% Al and 0.0002 to 0.0030% B, with the balance consisting of Fe and unavoidable elements.
A method for producing a high-strength hot-rolled steel sheet with excellent cold workability and surface quality, characterized by hot rolling at a temperature of r_3 or higher and winding the obtained hot-rolled steel strip at a temperature of 500°C or lower. . 7. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less N0.0050 % or less Sol. In addition to Al0.002-0.10% B0.0002-0.0030%, it contains one or two types of Ti or Nb in the range of 0.01-0.2% and 0.005-0.2%, respectively. Then, the steel consisting of the balance Fe and unavoidable elements was heated to Ar_
The hot rolled steel strip obtained by hot rolling at a temperature of 3 or more is
A method for producing a high-strength hot-rolled steel sheet with extremely excellent cold workability, characterized by winding at a temperature of 00°C or lower. 8. By weight: C0.0005-0.015% Mn0.05-0.5% S0.001-0.030% Cu1.0-2.2% P0.200% or less Si1.0% or less Ni0.15 ~1.0% N0.0050% or less Sol. In addition to Al0.002-0.10% B0.0002-0.0030%, it contains one or two types of Ti or Nb in the range of 0.01-0.2% and 0.005-0.2%, respectively. Then, the steel consisting of the balance Fe and unavoidable elements was heated to Ar_
The hot rolled steel strip obtained by hot rolling at a temperature of 3 or more is
A method for producing a high-strength hot-rolled steel sheet with extremely excellent cold workability, characterized by winding at a temperature of 00°C or lower. 9. The method according to any one of claims 5 to 8, which provides extremely excellent cold workability, characterized in that the coiling temperature after hot rolling is 350°C or lower and 100°C or higher. .
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7033789A JP2732885B2 (en) | 1988-10-24 | 1989-03-24 | High strength hot rolled steel sheet excellent in cold workability and surface quality and method for producing the same |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP26615988 | 1988-10-24 | ||
JP63-266159 | 1988-10-24 | ||
JP7033789A JP2732885B2 (en) | 1988-10-24 | 1989-03-24 | High strength hot rolled steel sheet excellent in cold workability and surface quality and method for producing the same |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH02194146A true JPH02194146A (en) | 1990-07-31 |
JP2732885B2 JP2732885B2 (en) | 1998-03-30 |
Family
ID=26411497
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Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP7033789A Expired - Fee Related JP2732885B2 (en) | 1988-10-24 | 1989-03-24 | High strength hot rolled steel sheet excellent in cold workability and surface quality and method for producing the same |
Country Status (1)
Country | Link |
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JP (1) | JP2732885B2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100782786B1 (en) * | 2001-12-26 | 2007-12-05 | 주식회사 포스코 | MANUFACTURING METHOD OF Cu CONTAINING HOT ROLLED STEEL SHEET WITH GOOD SURFACE QUALITY |
CN111690871A (en) * | 2019-03-13 | 2020-09-22 | 上海梅山钢铁股份有限公司 | Hot-rolled steel plate for cold-rolled electro-galvanized steel plate and manufacturing method |
-
1989
- 1989-03-24 JP JP7033789A patent/JP2732885B2/en not_active Expired - Fee Related
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100782786B1 (en) * | 2001-12-26 | 2007-12-05 | 주식회사 포스코 | MANUFACTURING METHOD OF Cu CONTAINING HOT ROLLED STEEL SHEET WITH GOOD SURFACE QUALITY |
CN111690871A (en) * | 2019-03-13 | 2020-09-22 | 上海梅山钢铁股份有限公司 | Hot-rolled steel plate for cold-rolled electro-galvanized steel plate and manufacturing method |
CN111690871B (en) * | 2019-03-13 | 2021-11-16 | 上海梅山钢铁股份有限公司 | Hot-rolled steel plate for cold-rolled electro-galvanized steel plate and manufacturing method |
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Publication number | Publication date |
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JP2732885B2 (en) | 1998-03-30 |
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